Thin-film flip-chip light emitting diode having roughening surface and method for manufacturing the same

ABSTRACT

A thin-film flip-chip light emitting diode (LED) having a roughened surface and a method for manufacturing the same are provided. First, a substrate having a patterned structure on a surface of the substrate is provided, and the surface is roughened. A first semiconductor layer is then formed on the surface; a light emitting structure layer is then formed on the first semiconductor layer; a second semiconductor layer is then formed on the light emitting structure layer. The first and second semiconductor layers possess opposite electrical characteristics. A first contact electrode and a second contact electrode are then formed on the first semiconductor layer and the second semiconductor layer, respectively. Finally, a sub-mount is formed on the first and second contact electrodes, and the substrate is removed to form the thin-film flip-chip LED having the roughened surface. Here, the light emitting efficiency of the thin-film flip-chip LED is improved.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 15/423,595, filed on Feb. 3, 2017, now issued as U.S. Pat. No.9,786,813, which is a divisional application of U.S. application Ser.No. 14/877,948, filed on Oct. 8, 2015, now issued as U.S. Pat. No.9,564,554. The prior application Ser. No. 14/877,948 claims the prioritybenefit of Taiwan application serial no. 103135236, filed on Oct. 9,2014. The entirety of each of the above-mentioned patent applications ishereby incorporated by reference herein and made a part of thisspecification.

FIELD OF INVENTION

The invention relates to a thin-film flip-chip light emitting diode(LED) with a roughened surface and a method for manufacturing thethin-film flip-chip LED. In particular, the invention relates to athin-film flip-chip LED that has a roughened surface and is formed byperforming a roughening process and a method for manufacturing thethin-film flip-chip LED. Through performing an etching process, a lightoutput surface of the thin-film flip-chip LED can be roughened, suchthat the light emitting efficiency of the thin-film flip-chip LED can beeffectively enhanced.

DESCRIPTION OF RELATED ART

Compared with conventional incandescent light sources, light emittingdiodes (LED) have the advantages of reduced power consumption,compactness, low driving voltage, the absence of mercury and thermalradiation, fast operating speed, and long service lives and are one ofthe power-saving light sources widely applied in next generation. Inparticular, the LEDs have been widely used as indicating lamps in homeappliances, used as back light sources of liquid crystal displays,applied to screens displaying graphics and texts, used as third brakelights on vehicles, and employed in other illumination fields.Semiconductor light emitting devices including resonant-cavity lightemitting diodes (RCLED), vertical-cavity surface-emitting diodes(VCSEL), and edge emitting laser are all available and effective lightemitting devices; however, the improvement of the light emittingefficiency of the LEDs is one of the issues to be resolved immediately,and thus various methods of improving the light emitting efficiency ofthe LEDs have been proposed.

According to the related art, e.g., in R.O.C. patent no. 1422068, themethod for manufacturing an LED having a roughened surface includes:providing an epitaxy component including a substrate, an epitaxystructure layer, and a first electrode layer, wherein the epitaxystructure layer is located on the substrate and includes a firstelectric type semiconductor layer, an active layer, and a secondelectric type semiconductor layer, the active layer is located betweenthe first and second electric type semiconductor layers, the firstelectric type semiconductor layer is located between the active layerand the substrate, and the first electrode layer electrically connectswith the first electric type semiconductor layer; etching a surface ofthe second electric type semiconductor layer with an excimer laserhaving an energy intensity of 1000 mJ/cm² or less to form a firstroughened surface including a plurality of first protrusions; performinga wet etching process on the first roughened surface to form a pluralityof second protrusions; forming a second electrode layer on the secondelectric type semiconductor layer. Present invention enhances the lightextraction efficiency of a light output surface of the LED as well as toreduce the operating voltage. However, the LED manufactured by applyingsaid manufacturing method may encounter the issue of process complexity.Besides, it is rather difficult to control the wet etching processperformed for roughening and shaping the second protrusions; thus, thedimensions of the resultant second protrusions may not be accuratelydetermined, and the final structure may be uneven. Moreover, accordingto the disclosure of the aforesaid patent, the roughening process isperformed after the thin films are stacked and the components are formedand shaped; as such, the underlying structure that is already formed maybe affected, and further the electrical behavior of the LED may beaffected as well, leading to a reduction of the light emittingefficiency of the LED. As a result, how to manufacture an even LEDstructure by performing a simple manufacturing process and how toenhance the light emitting efficiency of the resultant LED are importantissues to be resolved by researchers in the LED and pertinent fields.

SUMMARY

The invention is directed to a thin-film flip-chip light emitting diode(LED) with a roughened surface and a method for manufacturing thethin-film flip-chip LED. In particular, the invention relates to athin-film flip-chip LED with a roughened surface formed by performing aroughening process and a method for manufacturing the thin-filmflip-chip LED. Through performing an etching process, a light outputsurface of the thin-film flip-chip LED can be roughened, such that thelight emitting efficiency of the thin-film flip-chip LED can beeffectively enhanced.

A thin-film flip-chip LED having a roughened surface and a method formanufacturing the same are provided. In the method, at least followingsteps are included. A substrate is provided, and the substrate has apattern structure on its surface. The surface having the patternstructure is roughened. A first semiconductor layer is formed on thesurface having the pattern structure, a light emitting structure layeris formed on the first semiconductor layer, and a second semiconductorlayer is formed on the light emitting structure layer. The secondsemiconductor layer and the first semiconductor layer possess oppositeelectrical characteristics. A first contact electrode and a secondcontact electrode are formed on the first semiconductor layer and thesecond semiconductor layer, respectively. A sub-mount is formed on thefirst and second contact electrodes, and the substrate is removed, so asto form the thin-film flip-chip LED having the roughened surface.

In an embodiment of the method for manufacturing the thin-film flip-chipLED, the method of roughening a surface of a first protrusion is carriedout by performing an etching process.

In an embodiment of the method for manufacturing the thin-film flip-chipLED, the etching process is excimer laser etching, dry etching, or wetetching.

In an embodiment of the method for manufacturing the thin-film flip-chipLED, the first protrusion is a cone.

In an embodiment of the method for manufacturing the thin-film flip-chipLED, the cone is a circular cone, a triangular pyramid, or aquadrangular pyramid.

In an embodiment of the method for manufacturing the thin-film flip-chipLED, the substrate is selected from the group consisting of sapphire(Al₂O₃), silicon carbide (SiC), silicon (Si), gallium arsenide (GaAs),zinc oxide (ZnO), and a hexagonal crystal material.

In an embodiment of the method for manufacturing the thin-film flip-chipLED, the light emitting structure layer has a multi-quantum well (MWQ)structure. The MWQ structure includes a plurality of well layers andbarrier layers, the well layers and the barrier layers are alternatelystacked, and every two of the barrier layers have one well layer inbetween.

The invention further provides a thin-film flip-chip LED having aroughened surface formed by performing the manufacturing methoddescribed in the previous embodiments. The thin-film flip-chip LED atleast includes a sub-mount, a first contact electrode, a second contactelectrode, a second semiconductor layer, a light emitting structurelayer, and a first semiconductor layer. The first contact electrode isarranged on the sub-mount, the second contact electrode is arranged onthe sub-mount and located corresponding to the first contact electrode,the second semiconductor layer is formed on the second contactelectrode, the light emitting structure layer is formed on the secondsemiconductor layer, and the first semiconductor layer iscorrespondingly formed on the first contact electrode and the lightemitting structure layer. Here, plural roughened patterned structuresare formed on a surface of the first semiconductor layer away from thelight emitting structure layer.

In an embodiment of the thin-film flip-chip LED, the patternedstructures are circular cones, triangular pyramids, or quadrangularpyramids.

In an embodiment of the thin-film flip-chip LED, a gap exists betweenevery two of the patterned structures.

As provided above, in the thin-film flip-chip LED having the roughenedsurface and the method for manufacturing the thin-film flip-chip LED,the etching process is performed to form the roughened surface with dualcones on the substrate, so as to ensure both the improved light outputefficiency of the light beam emitted from the light emitting structurelayer of the thin-film flip-chip LED and the simplicity of the processof manufacturing the thin-film flip-chip LED. In addition, the excimerlaser process serves as the second roughening process performed on thepatterned substrate, so as to resolve the issue of inconsistentdimensions of the structure resulting from wet etching and enhance thelight emitting efficiency of the thin-film flip-chip LED. Finally,different from the conventional LED and the conventional manufacturingprocess of the LED, i.e., performing the roughening process after filmdeposition and manufacture of the components, in the thin-film flip-chipLED having the roughened surface and the method for manufacturing thethin-film flip-chip LED, the patterned substrate is firstly formed onthe substrate, and the roughening process is performed on the patternedsubstrate, which may effectively prevent thin films and components frombeing damaged by the subsequent roughening process, protect theelectrical behavior of the LED, and effectively enhance the lightemitting efficiency of the LED.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating steps of manufacturing a thin-filmflip-chip LED with a roughened surface according to an embodiment of theinvention.

FIG. 2 is a schematic cross-sectional view illustrating a substrate witha patterned structure according to an embodiment of the method formanufacturing the thin-film flip-chip LED with the roughened surface.

FIG. 3 is a schematic cross-sectional view illustrating stacked thinfilms according to an embodiment of the method for manufacturing thethin-film flip-chip LED with the roughened surface.

FIG. 4 is a schematic view of shaping electrodes according to anembodiment of the method for manufacturing the thin-film flip-chip LEDwith the roughened surface.

FIG. 5 is a schematic view of shaping a sub-mount and removing asubstrate according to an embodiment of the method for manufacturing thethin-film flip-chip LED with the roughened surface.

FIG. 6 is a schematic view illustrating gaps in a roughened structureaccording to another embodiment of the method for manufacturing thethin-film flip-chip LED with the roughened surface.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS

The structural design and functions will be provided in the embodimentsof the invention as illustrated in the drawings below for betterunderstanding the invention.

First, in the following embodiments, it should be understood that thedescription of one layer (or film) or one structure arranged “on” or“below” another substrate, another layer (or film), or another structuremay include the following: one layer (or film) or one structure is“directly” located on another substrate, another layer (or film), oranother structure; one or more inter-layer is “indirectly” arrangedbetween the layers (or films) or the structures. The location of eachlayer may be observed in the drawings.

First, as shown in FIG. 1 to FIG. 3, which are respectively a flowchartillustrating steps of manufacturing a thin-film flip-chip LED with aroughened surface according to an embodiment of the invention, aschematic cross-sectional view illustrating a substrate with a patternedstructure, and a schematic cross-sectional view illustrating stackedthin films, the method for manufacturing the thin-film flip-chip LEDwith the roughened surface provided herein includes following steps.

Step 1 (S1): providing a substrate (1), a surface of the substrate (1)having a patterned structure (11). The substrate (1) is selected frontthe group consisting of sapphire (Al₂O₃), silicon carbide (SiC), silicon(Si), gallium arsenide (GaAs), zinc oxide (ZnO), and a hexagonal crystalmaterial; an embodiment of the invention, the substrate (1) is made of aAl₂O₃ material. The patterned structure (11) on the substrate (1) may beformed by performing a photolithography process and an etching process,so as to form a patterned substrate with consistent dimensions. Thepatterned structure (11) is a cone, and the cone may be a circular cone,a triangular pyramid, or a quadrangular pyramid.

Step 2: roughening the surface having the patterned structure (11). Thestep of roughening the surface having the patterned structure (11) iscarried out by performing the etching step, and the etching step isexcimer laser etching, dry etching, or wet etching. In embodiment of theinvention, the excimer laser is applied to roughening the surface havingthe patterned structure (11). The excimer laser includes KrF excimerlaser, KrCl excimer laser, ArF excimer laser, XeCl excimer laser, or XeFexcimer laser. With use of one of the above-mentioned excimer lasers,the step of roughening the surface having the patterned structure (11)is carried out. However, note that the type of the excimer lasersprovided above is merely exemplary and should not be construed as alimitation to the invention; people skilled in the pertinent art shouldknow different types of excimer lasers applied to roughen the surfacehaving the patterned structure (11) are not factors of affecting theimplementation of the invention.

Step 3 (S3): forming a first semiconductor layer (2) on the surface ofthe substrate having the patterned structure (11). In an embodiment ofthe invention, the first semiconductor layer (2) is an n-typesemiconductor layer and is coated onto the roughened surface of thesubstrate having the patterned structure (11) through metal-organicchemical vapor deposition (MOCVD).

Step 4 (S4): forming a light emitting structure layer (3) on the firstsemiconductor layer (2). In an embodiment of the invention, the lightemitting structure layer (3) has an MWQ structure, and the MWQ structureincludes a plurality of well layers (31) and barrier layers (32). Thewell layers (31) and the barrier layers (32) are alternately stacked,and every two of the barrier layers (32) have one of the well layers(31) in between. The light emitting structure layer (3) is also formedon the first semiconductor layer (2) through MOCVD.

Step 5 (S5): forming a second semiconductor layer (4) on the lightemitting structure layer (3), wherein the second semiconductor layer (4)and the first semiconductor layer (2) possess opposite electricalcharacteristics. In an embodiment of the invention, the secondsemiconductor layer (4) is a p-type semiconductor layer which possesseselectrical characteristics opposite to those of the first semiconductorlayer (2) which is an n-type semiconductor layer, and the secondsemiconductor layer (4) is also formed on the light emitting structurelayer (3) through MOCVD.

Step 6 (S6): forming a first contact electrode (5) and a second contactelectrode (6) on the first semiconductor layer (2) and the secondsemiconductor layer (4), respectively. Please refer to FIG. 4 that is aschematic view of shaping electrodes according to an embodiment of themethod for manufacturing the thin-film flip-chip LED with the roughenedsurface. Before the first contact electrode (5) and the second contactelectrode (6) are formed and shaped, partial regions of the secondsemiconductor layer (4) and the light emitting structure layer (3) areremoved by performing a photolithography process and an etching process,so as to expose the first semiconductor layer (2). The first contactelectrode (5) and the second contact electrode (6) are then respectivelyformed on the first semiconductor layer (2) and the second semiconductorlayer (4) in an ohmic-contact manner. In an embodiment of the invention,the first contact electrode (5) in contact with the first semiconductorlayer (2) that is an n-type semiconductor layer is an n-type electrode,and the second contact electrode (6) in contact with the secondsemiconductor layer (4) that is a p-type semiconductor layer is a p-typeelectrode.

Step 7 (S7): forming a sub-mount (7) on the first contact electrode (5)and the second contact electrode (6) and removing the substrate (1), soas to manufacture the thin-film flip-chip LED having the roughenedsurface. Please refer to FIG. 5 that is a schematic view of shaping asub-mount and removing a substrate according to an embodiment of themethod for manufacturing the thin-film flip-chip LED with the roughenedsurface. Here, a laser lift-off (LLO) technique may be applied to removethe substrate (1) made of the Al₂O₃ material. Since the LLO technique iswell known in the pertinent field, no further description is providedhereinafter. Additionally, a transparent sub-mount (7) is formed on thefirst contact electrode (5) and the second contact electrode (6) thathave planes with the same altitude, which is one of the main technicalfeatures of the flip chip LED.

The invention further provides a thin-film flip-chip LED with aroughened surface, and the thin-film flip-chip LED is formed byperforming the above-mentioned manufacturing method. With reference toFIG. 5, the thin-film flip-chip LED with the roughened surface at leastincludes:

a sub-mount (7);

a first contact electrode (5) arranged on the sub-mount (7);

a second contact electrode (6) arranged on the sub-mount (7) and locatedcorresponding to the first contact electrode (5);

a second semiconductor layer (4) formed on the second contact electrode(6), wherein in an embodiment of the invention, the second semiconductorlayer (4) and the second contact electrode (6) are electricallyconnected in an ohmic-contact manner, and in an embodiment of theinvention, the second semiconductor layer (4) is a p-type semiconductorlayer, and the second contact electrode (6) is a p-type electrode;

a light emitting structure layer (3) formed on the second semiconductorlayer (4), wherein the light emitting structure layer (3) has an MWQstructure, the MWQ structure includes a plurality of well layers (31)and barrier layers (32), the well layers (31) and the barrier layers(32) are alternately stacked, and every two of the barrier layers (32)have one of the well layers (31) in between;

a first semiconductor layer (2) correspondingly formed on the firstcontact electrode (5) and the light emitting structure layer (3),wherein plural roughened patterned structures are formed on a surface ofthe first semiconductor layer (2) away from the light emitting structurelayer (3). In an embodiment of the invention, the first semiconductorlayer (2) is an n-type semiconductor layer having the electricalcharacteristics opposite to those of the second semiconductor layer (4),and the first contact electrode (5) electrically connected to the firstsemiconductor layer (2) in an ohmic-contact manner is an n-typeelectrode. Besides, the roughened patterned structure is formed on thesurface of the first semiconductor layer away from the light emittingstructure layer (3) (i.e., the light output surface of the thin-filmflip-chip LED having the roughened surface as provided herein) byperforming dual-etching processes that may be excimer laser etching, dryetching, or wet etching. Thereby, the thin-film flip-chip LED having theroughened surface can have the improved light emitting efficiency.

Besides, as shown in FIG. 6, which is a schematic view illustrating gapsin a roughened structure according to another embodiment of the methodfor manufacturing the thin-film flip-chip LED with the roughenedsurface, gaps with the same length exist between every two of thepatterned structures (11) respectively having the roughened structure(12), which may also enhance the light emitting efficiency of thethin-film flip-chip LED having the roughened surface as provided herein.

In light of the foregoing embodiments, compared to the related art, thethin-film flip-chip LED having the roughened surface and the method formanufacturing the thin-film flip-chip LED have following advantages.

1. In the thin-film flip-chip LED having the roughened surface and themethod for manufacturing the thin-film flip-chip LED, the etch processis performed to form the roughened surface shaped as dual cones on thesubstrate; thereby, the light beam emitted from the light emittingstructure of the thin-film flip-chip LED may be characterized by theimproved light emitting efficiency, and the method for manufacturing thethin-film flip-chip LED is characterized by its simplicity.

2. In the thin-film flip-chip LED having the roughened surface and themethod for manufacturing the thin-film flip-chip LED, the secondroughening process is performed on the patterned substrate by means ofexcimer laser, thereby rectifying the defects of inconsistent dimensionsof the structure caused by wet etching and enhancing the light emittingefficiency of the thin-film flip-chip LED.

3. Different from the conventional LED and the conventionalmanufacturing process of the LED, i.e., performing the rougheningprocess after film deposition and manufacture of the components, in thethin-film flip-chip LED having the roughened surface and the method formanufacturing the thin-film flip-chip LED, the patterned substrate isformed on the substrate, and the roughening process is then performed onthe patterned substrate, which may effectively prevent thin films andcomponents from being damaged by the subsequent roughening process,protect the electrical behavior of the LED, and effectively enhance thelight emitting efficiency of the LED.

What is claimed is:
 1. A method for manufacturing a light emittingdiode, comprising: providing a substrate having a patterned structurethereon; etching the substrate; forming an epitaxial structurecomprising a first semiconductor layer formed on the patterned structureof the substrate, a light emitting structure layer formed on the firstsemiconductor layer and a second semiconductor layer formed on the lightemitting structure layer, wherein the first semiconductor layer and thesecond semiconductor layer possess opposite electrical characteristics;forming a sub-mount on the epitaxial structure; removing the substratefrom the epitaxial structure to expose a surface of the firstsemiconductor layer; and etching the surface of the first semiconductorlayer to form a roughened structure thereon.
 2. The method formanufacturing the light emitting diode of claim 1, wherein the step foretching the substrate is performed by excimer laser etching, dryetching, or wet etching.
 3. The method for manufacturing the lightemitting diode of claim 1, wherein the step for removing the substratefrom epitaxial structure is performed by laser lift-off process.
 4. Themethod for manufacturing the light emitting diode of claim 1, whereinthe step for etching the surface of the first semiconductor layer isperformed by excimer laser etching, dry etching, or wet etching.
 5. Themethod for manufacturing the light emitting diode of claim 1, whereinthe substrate is selected from the group consisting of sapphire, siliconcarbide, silicon, gallium arsenide, zinc oxide, and a hexagonal crystalmaterial.
 6. The method for manufacturing the light emitting diode ofclaim 1, wherein the light emitting structure layer has a multi-quantumwell structure, the multi-quantum well structure comprises a pluralityof well layers and barrier layers, the well layers and the barrierlayers are alternately stacked, and every two of the barrier layers haveone of the well layers in between.
 7. A method for manufacturing a lightemitting diode, comprising: providing a sub-mount; forming an epitaxialstructure on the sub-mount, wherein the epitaxial structure comprising afirst semiconductor layer, a light emitting structure layer formed onthe first semiconductor layer and a second semiconductor layer formed onthe light emitting structure layer, wherein the first semiconductorlayer and the second semiconductor layer possess opposite electricalcharacteristics, wherein a surface of the first semiconductor layer awayfrom the sub-mount is exposed; and etching the surface of the firstsemiconductor layer to form a roughened structure thereon.
 8. The methodfor manufacturing the light emitting diode of claim 7, wherein the stepfor etching the surface of the first semiconductor layer is performed byexcimer laser etching, dry etching, or wet etching.
 9. The method formanufacturing the light emitting diode of claim 7, wherein the lightemitting structure layer has a multi-quantum well structure, themulti-quantum well structure comprises a plurality of well layers andbarrier layers, the well layers and the barrier layers are alternatelystacked, and every two of the barrier layers have one of the well layersin between.
 10. A method for manufacturing a light emitting diode,comprising: providing a substrate; forming an epitaxial structurecomprising a first semiconductor layer formed on the patterned structureof the substrate, a light emitting structure layer formed on the firstsemiconductor layer and a second semiconductor layer formed on the lightemitting structure layer, wherein the first semiconductor layer and thesecond semiconductor layer possess opposite electrical characteristics;mounting the epitaxial structure with the substrate to a sub-mount;removing the substrate from the epitaxial structure to expose a surfaceof the first semiconductor layer; and etching the surface of the firstsemiconductor layer to form a roughened structure thereon.
 11. Themethod for manufacturing the light emitting diode of claim 10, whereinthe step for removing the substrate from the epitaxial structure isperformed by laser lift-off process.
 12. The method for manufacturingthe light emitting diode of claim 10, wherein the step for etching thesurface of the first semiconductor layer is performed by excimer laseretching, dry etching, or wet etching.
 13. The method for manufacturingthe light emitting diode of claim 10, wherein the substrate is selectedfrom the group consisting of sapphire, silicon carbide, silicon, galliumarsenide, zinc oxide, and a hexagonal crystal material.
 14. The methodfor manufacturing the light emitting diode of claim 10, wherein thelight emitting structure layer has a multi-quantum well structure, themulti-quantum well structure comprises a plurality of well layers andbarrier layers, the well layers and the barrier layers are alternatelystacked, and every two of the barrier layers have one of the well layersin between.